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krb5: Fix(?) st_nlink check in fcache.c

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We have a check for symlinks and hardlinks so that we refuse to open
ccaches through symlinks or which have hardlinks.  This check is too
strict, checking for `st_nlink != 1`, which runs into trouble when a
ccache is mounted as a file into a container, in which case `stat(2)`
reports it as having zero links.

The fix is to check for `st_nlink > 1`:

    -    if (sb2.st_nlink != 1) {
    +    if (sb2.st_nlink > 1) {
            krb5_set_error_message(context, EPERM, N_("Refuses to open hardlinks for caches FILE:%s", ""), filename);

Though I question the utility of the hardlink check.  MIT Kerberos
doesn't have it.
This commit is contained in:
Nicolas Williams
2022-12-29 22:27:42 -06:00
parent f4fd02b810
commit 58e07f8882
1 changed files with 1 additions and 1 deletions
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2
lib/krb5/fcache.c
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@@ -581,7 +581,7 @@ again:
* locations on tmpfs "run" directories. But we don't know here
* that this is the case. Thus: no hard-links, no symlinks.
*/
if (sb2.st_nlink != 1) {
if (sb2.st_nlink > 1) {
krb5_set_error_message(context, EPERM, N_("Refuses to open hardlinks for caches FILE:%s", ""), filename);
close(fd);
return EPERM;